The subject invention relates generally to an electronic assembly containing flip chip components on a laminate circuit board within the electronic assembly and, more particularly, to an apparatus and method of providing a relaxed tolerance assembly for the flip chip components and laminate circuit board with respect to heat dissipating structures of the assembly.
A variety of methods are known for dissipating heat generated by semiconductor devices. In the case of semiconductor devices mounted on a circuit board and mounted within an enclosure, thermal management is usually achieved by dissipating heat primarily in the vertical direction, both above and beneath the semiconductor device. For example, heat-generating semiconductor chips, such as power flip chips, are often mounted to alumina substrates that conduct and dissipate heat in the vertical direction away from the chip.
One form of assembly utilizes a housing having a plurality of heat sink devices in the form of pedestals that are adapted to be both above and below the flip chip when the housing is assembled. The flip chips are made to come into contact with the pedestals through contact pressure. Additionally, thermal grease is used between the flip chip and the pedestal. The thermal grease provides a conductive path between the heat sink and the flip chip. The thermal grease also protects the flip chip due to the contact pressure required to maintain the heat sink to the flip chip for proper thermal contact.
This type of enclosure and/or heat dissipating method, however, requires fairly close tolerances. Particularly, these systems require fairly precise measurement and control.
It is an object of the subject invention to provide a system, method and/or apparatus for conducting heat from a flip chip semiconductor device mounted to a substrate that requires less tolerance in providing thermal contact between the flip chip and the heat dissipating structure or heat sink.
It is another object of the subject invention to provide a system, method and/or apparatus for conducting heat from a flip chip assembly that minimizes critical height tolerance requirements between a flip chip and a heatsink pedestal.
It is yet another object of the subject invention to provide a system, method and/or apparatus for conducting heat from a flip chip assembly that does not require thermal grease.
In accordance with a preferred embodiment of the subject invention, these and other objects and advantages are accomplished as follows.
According to the subject invention, there is provided a system, method and/or apparatus or assembly for conducting heat from a flip chip semiconductor device such as a power flip chip.
In one form, there is provided a heat-dissipating assembly for removing heat from a flip-chip semiconductor device. The assembly includes a housing having a thermally-conductive first housing portion and a second housing portion, a flexible substrate supported within the housing, the substrate having conductors thereon, a flip chip mounted to the substrate, the flip chip having a first surface and solder bumps on the first surface registered with the conductors on the substrate, the flip chip having a second surface oppositely disposed from the first surface, a first heat sink extending inwardly towards the flip chip from the first housing portion; and a first pre-cured silicone adhesive layer disposed on an end of the first heat sink and in thermal relationship with the second surface of the flip chip.
In another aspect of the invention, the first and second housing portions are provided with a joint configured to control the pressure exerted on the flip chip through the heat sink components. In one embodiment, the flip chip is mounted between heat sink pedestals connected to the first and second housings. The joint between the housings controls the travel of the two housings toward each other when the assembly is put together. More particularly, the joint prevents excessive travel of the heat sink pedestals toward each other, which might damage the flip chip entrained between the pedestals.
In another form, the subject invention provides a method for conducting heat from a flip chip, the method including the steps of: (a) providing a flexible substrate having conductors thereon, a flip chip having a first surface with solder bumps on the first surface and a second surface oppositely disposed from the first surface, the flip chip being mounted to the substrate such that the solder bumps are registered with the conductors on the substrate; and (b) enclosing the substrate and flip chip within a housing so that a first pre-cured silicone adhesive disposed on a first heat sink contacts the second surface of the flip chip in a first thermal transfer relationship.
Other objects and advantages of this invention will be appreciated from the following detailed description.